用户选择一个颜色，获取反转的颜色
<!doctype html>
<html>
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width,initial-scale=1, maximum-scale=1 ">
    <meta name="apple-mobile-web-app-capable" content="yes">
    <meta name="apple-mobile-web-app-status-bar-style" content="black">
    <title>颜色反转</title>
<style>
div{
    width:200px;
    height:80px;
    background-color:#000;
    color:#fff;
    font-size:20px;
    text-align:center;
    line-height:80px;
}
</style>
<script>
    function hexToReverse(h) {
        var r = 0, g = 0, b = 0;
        r = 255 - parseInt(h[0],16)*16 - parseInt(h[1],16);
        g = 255 - parseInt(h[2],16)*16 - parseInt(h[3],16);
        b = 255 - parseInt(h[4],16)*16 - parseInt(h[5],16);
        return (r < 16 ? "0" + r.toString(16).toUpperCase() : r.toString(16).toUpperCase()) + (g < 16 ? "0" + g.toString(16).toUpperCase() : g.toString(16).toUpperCase()) + (b < 16 ? "0" + b.toString(16).toUpperCase() : b.toString(16).toUpperCase());
    }
    function getReverseColor(){
        var a = document.getElementById("choiceColor");
        var bg_str  =a.value;
        var font_str = "#"+hexToReverse(bg_str.replace("#",""));
        var aa=document.getElementById("aa");
        aa.style.backgroundColor = bg_str;
        aa.style.color = font_str;
        //alert("背景颜色："+bg_str);
        //alert("文字颜色："+font_str);
    }
</script>
</head>
<body>
请选择主色（背景色）<input type="color" id="choiceColor"/><input type="button" value="反转"  onclick="getReverseColor();"/>
<div id="aa">我是反转后的辅色</div>
</body>
</html>